Ultra Intelligence: Impact on Actual Military Campaigns

Figure 1.--

Ultra had a significant impact on several major military campaigns. The Bletchely Park codebreakers began to crack Enigma codes at a very early point of the War (January 1940) and additional progress followed rapidly after that. Developing systems to evaluate and interpret the decrypts and then to deseminate actionable inteligence to military commands. As a result, although Bletchely Park was developed detailed information on the German Western offensive (May 1940), systems were not in place to get useful information to field units nor were field commands ready to accept the accuracy of the information provided, in part because the source was obscured by passing it off as MI6 espionage. Some commanders were afraid that it might be enemy disinformation. This gradually changed as commanders learned how accurate and reliable the ingormation was. The Ultra decrypts would have a major impact on the North African campaign. The greatest problem proved to be the naval Enigmas, but ultumately this proved to be some of the most valuable information. Ultra had a major role in preparing for D-Day. The greatest failure was the German Bulge offensive, but the failure here was more of command failure to use Ulta than the Blethley Park code breakers as well as German signals discipline.

Scandanavia Campaign (April 1940)

Germany launched an invasion of Denmark and Norway (April 1940). Denmark which bordered on the Reich was occupied within hours, Norway was a muvh more difficult opetration, involving a complicated naval and air operation. The progress already made at Bletchely Park was rewarded by thge cracking of tghe Enigma 'Yellow' cypher. The result was a flood of decrypts for which the Bletchely Park code breakers nor the military commands were not prepared. The decrypts revealed just about every detail of the German operations and the units involved. Tragically the Norwegian milutary was not only small, but totally unprepared so there was little ability to react. The Allies did react, but Bletchely Park was not yet prepared to assess and deseminated actionable information from the flood of decrypts delivered by the code breakers. The small group of intelligence officers at Bletchley Park were overwhelmed. The details on code names, German units, and movements were impossible to assess quickly by the small staff in place. And in addition there was no system in place for delivering inteligence reports to the appropriate military commands. [Smith] This of course had to be done carefully to preserve the integrity of the Ultra secret. As a result, the Ultra decrypts had no impact on the Scandinavian campaign. Fighting continued in the north, but the Allies withdrew when the storm broke in the West.

German Western Offensive (May-June 1940)

The Germans launched their long-awaited Western offensive (May 1940). They quickly defeated the Dutch and then as the British Expeditionary Fiorce entered Belgium to try to reach the Dutch, the Germand struck in the Ardennes an broke through French lines by crossing the Meuse in force. This began the drive to the Channel, cutting off the BEF and French 1st Division. By this time, the British were in the process up setting Special Liaison Units to deliver Bletchley Park Ultra intelligence to field commanders in the field. The systtem was still just being estanlished when the Germans struck. This and the fact that the primary fighting force was the French Army meant that Ultra had no real imoact on the campaign.

Battle of Britain (July 1940 - May 1941)

The Battle of Britain of course was a critical momment of the War. The Germans were at the height of their power and the British Army largely unarmed, having left theur equipment at Dunkirk. The issue would be settled by a small force of still inexperienced RAF figher pilots who needed all the help they could get. The RAF liaison nets were fed a great deal of valuable information usung the Red cypher. This ptovided valuable information on German plans, disposition, and operations. While the information could not be effectively used in the Battke for France, it was in the Battle of Britain. Bletchley Park for a time lost the critical Red cypher. A student named John Herivel developed a system that helped break back in (May 1940). [Smith] This proved too late for the Battle for France, but did mean that by the time of the Battle of Britain that Bletchley Park was producing some Luftwaffe decrypts. The deciphering process was still quite slow, usually about 48 hours which limited the utility of the decrypts. It was not until 1941 that Bletchely Park was able to produce really timely decrypts, by which time the critical phase of the Bttle had passed. Another limitation was that at the time of the Battle of Britain, Ultra was still a work in progress. And decrypting the messages was only part of the process. The other key step was working out how to get the information to the appropriate military commznds without endangering the secret that Enigma messages were being cracked. Unfoirtunstely, Ultra was kept a secret for mny years after the War. Thus historians did not address this subject while a clear picture could be easily built. It is believed that only Air Chief Marshall Hugh Dowding and Air Vice Marshal Keith Park received Ultra Decrypts through much of the Battle. Recent work suggests that Dowding was only informed of Ultra (October 16, 1940). [Gilbert] This of course was after the important air battles. There are disagreements among historians over Ultra's importance in the Battle of Britain. Quite a number of historians have concluded that Ultra waa not a major factor in the battle. [Ray, p. 59.] Other historians contended that it was useful in providing important insights to Luftwaffe Chief Göring's intentions. F. W. Winterbotham, an air intelligence office, insists that Ultra provided precise warning of the massed attacks by Luftflotten 2, 3, and 5 (August 15). Winterbotham reports that Dowding told him that Ultra was of the greatest help to him to know what Goering's intentions were and helped him use his fighter squadrons with the greatest economy when the Luftwaffe had planned thec raids to streach the fighter cover. [Bickers, p. 59.] Other historians point out times when Fighter Command was surprised by attacks on Kenley and Biggin Hill (August 18) and more importantly when Göring began the Blitz on London (september 7). These descrepancies may not be as telling as they appear. Bletchely Park was still not sucessfully decrypting sll the messages received or decrypting them in a timely fassion. But the assessment of the role of Ultra in the Battle is still not well established. Besides actual opertional intelligence, Ultra along with other sources was creating a detailed assessment of the Luftwaffe order of battle. The British throughout the Battle had a much better handle on Luftwaffe deployment abd strength that the Luftwaffe had on the RAF.

Mediterranean Naval Campaign (1940-41)

With France defeated, the Royal Navy with its battle fleet primarily deployed un the North Atlantic and North Sea could not spare many ships for its Meditwrranean squadron. And they would have to fight it out with the powerful Italian Fleet. The first tactical victory from an Enigma intercept came at Cape Matapan (March 1941). [Budiansky, pp. 183-86.]

Opertion Barbarossa (June-December 1941)

The Ultra system was too new to be of assistance to the Allies in the Norwegian (April 1940) and Western campaigns(May 1940). Barbarossa was different. Both the British and Americans learned what the Germans were preparing to do. We are not sure just when the Bletchley crytptologists concluded what the Germans were preparing and informed Primeminister Churchill. One source suggests the British had some inkling of Hitler's intentions even during the Battle of Britain (August 1940). Wehrmacht planners had a basic plan for Barbarossa (December 1940). And the troop deployments west began soon after that. As Ultra was fully operationsl by that point and given the dimensions of the opertations, Bletchly Park would have learned early in 1941. This information must be known and discussed in the many books on Bletchley Park and Ultra, but we have not yet found it. We know that Bletchley Park decoded Führer Dirctive 21 (Operation Barbarossa) (December 1940). And that Wehrmacht decrypts must have shown a massive deployment east whoich cold have been for only one purpose. The British were leaking information on the German buldup to the Soviets for weeks before Hitler launched Barbarossa. The British forwarded information indicrectly through agents in Switzerland and Eastern Europe in an effort to desguise the work at Bletchley Park and the Ultra secret. Both the British and Americans warned Stalin without revealing their sources. Churchill sent a personal telegram to Stalin (June 11). Direct contacts through the British Embassy in Moscow are mired in controversy, in part because British Ambassador Sir Stafford Cripps did not want to pass on the warnings. [Gorodetsky, p. 979.] The Americans also learned of the invasion and warned Stalin. Sam Woods at the U.S. Embassy in Berlin began to collect information about German intentions in the East (late-July 1940). The reports were discounted in Washington. Later Purple decrypts of mesages between Tokyo and Japanese Embassy in Berlin confirmed Woods' work. President Roosevelt ordered that the Soviet Government be iformed. Under-Secretary of state Sumnr Wells personlly notified SovietAmbassador Umansky in washington (March 20). The state Department cbeled Anbassador Laurence Steinhartin Moscow. When the translation reached Stlin, he wrote 'Provication!' on it. Steinhart conveyed subsequent warnings to Soviet officials. [Murphy, p. 146.] Stalin was getting similar warnings from his own iteligence sources and reports of German troop dispositioins. He chose to ignore all these warnings. [Lewin] Stalin was convinced that the British and Americans were trying to draw him into the War and until the actual attack could not believe that Hitler would attack him. The German attack, as a result, was an enormous strategic, tactical, and operational success. The Soviets were surprised and devestated. German formations drove deep into the Soviet Union and destroyed or captured a sunstantial part of the Red Army. Stalin was shocked and descened ito a near-catatonic state at his dachau. He refused to emerge and speak to the Soviet people for 2 weeks. The country was virtually leaderless during this critical period. Ultra could have helped the Soviets prepare for the German attack. But as a result of Stlin's paranoia, this warning which could have had had a major impact on the War was lost. The Allies subsequently proivided the Soviets Ultra intelligence, but without devulging the source. Given the accuracy and timliness of the inteligence provuided, the Sovirts must have realized at some point that the Allies had cracked Enigma. Soviet inteligence sources believed that the Americans had broken the Japanese diplmatic codes months before Pearl Harbor. It is interesting to note tht while the Allies attemppted to warn the Soviets, the Soviets who had intelligence tht the Japanese were prepating to strike in the Pacific, made no effort at warning either the Americans and British. And Soviet diplomts un learned that the Americans had cracked the Japanese Purple Code, alerted Japan's German allies.

North Africa (March 1941-May 1943)

The first camaign to be significantly impacted by Ultra was the fighting in the Western Desert. By this time the system at Bletchely Park for assessing the Enigna decrypts and delivering actionable inteligemnce reports was firmly in place. The problem at first was the commanders involved did not trust the reports. They were not told the true source of the inteligence. The cover story was that the information came from M16 espionage reports. Thus valuable intelligence was largely ignored. This changed with the desperate British facing the Afrika Korps within a few miles of Suez. Ultra provided the new British commander in the Western Desert, Bernard Montgomery, of the date an plan of attack for what would be Rommel's final offensive to break through to Suez (August 31, 1942). Bletchey had begun reading Rommell's Heer Enigma key (Chaffinch) with only a 1-day delay And the GCCS unit in Cairo was reading Scorppion a Luftwaffe key used for cooperation with the Heer. The battle of Alam el Haifa proved to be a disater for the Afrika Korps. When the Germans attacked they were first hit by RAF planes as they plunged in a British minefield. Then they faced, but were unable to take the Alam el Haifa Ridge where Montgi\omrybhad massed artillery and tanks. The battered Afrika Korps was forced to retreat. Ultimately the inteligence on Italian convoys would play a critical role in depriving the Afrika Korps of desparately needed supplies and equipment--especially oil. The major limitartion on the British interdictment campaign was the need to ensure that the Germans and Italians did not realize that their Enigma tranmissiins had been cracked.

Battle of the Atlantic

The Battle of the Atlantic along with the Soviet Eastern Front were the two most critical campaigns of the War. The Kriegsmarine was not ready for the War and did not fully preceive the effectiveness of the U-boats. This soon changed and the Germand began a crash oprogram to build new a better U-boats. All the Allied campaigns were premised on keeping vthe sea lanes to Britain open. Without supplies from America and the Dominions, Britain could not continue the war. And thus this all the subsequent Allied campaigns were impossible. Nor could have vital Lend Lease aid been delivered to the Sioviets to support the fighting on the Eastern Front. Bletchely Park Ultra intelligence was forwarded to the Admiralty through the Z Watch in the Naval Section. The Admiralty like the generals at first did not attach much importance to it. And of all the service Enigmas, Bletechkly Park had the greatest difficulty with the naval Enigmas. Gradually the Admiralty began to see the accuracy and importance of the Ultra intelligence. They were abke to track the U-Boat wolf packs. This enabked them to at first reroute convoys and evdbntually as naval strength grew and America enterd the War to attack not only Wolf Packs, but individual U-boats. , considerably reducing the German Navy's ability to sink the merchant navy ships bringing vital supplies to Britain from America.


Ultra had a major role in preparing for D-Day. A key part of the planning for D-Day was knowing the disposition of German forces, both what was on the beaches and what forces the Germans could bring forward once the landings took place. Ultra provided a detailed picture of the German order of battle. This combined with Resistance reoorts and air reconisance provided General Eisenhower and his planners perhaps the most detailed picture of an enemy force than any commander in history possessed before a major battle. In contrast the Germans knew virtually noyhing avout the Allied preparations and forces being assemmbled in the Chanbnel ports.

Market Garden

Battle of the Bulge

The greatest Ultra failure was the German Bulge offensive, but the failure here was more of command failure to use Ulta than the Blethley Park code breakers as well as German signals duscipline.


Bickers, Richard Townshend. Battle of Britain (Salamander, 1999).

Budiansky, Stephen. Battle of Wits: The Complete Story of Codebreaking in World War II (Simon and Schuster--Touchstone: New York, 2002), 436p.

Gilbert, Martin. A History of the Twentieth Century Vol. 2 1933-54 (William Morrow and Company, Inc.: New York, 1998), 1050p.

Gorodetsky, Gabriel. "Churchill's warnings to Stlin: A reappraisal," The Historical Journal (December 1986). Vol. 29, No. 4, pp 979-90.

Lewin, Ronald Ultra goes to War (Penguin: London, 1978 and 2001).

Murphy, David E. What Stalin Knew: The Enigma of Barbarossa (Yale Press: New Haven, 2005), 310p.

Ray, John. Battle of Britain: New Perspectives (Arms & Armour Press, 1994).

Smith, Michael. Station X: The Code Breakers of Bletchley Park.


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Created: 4:14 PM 3/21/2011
Last updated: 7:44 PM 1/10/2013